Coleoptera: Carabidae) Assemblages Within a New York State Wetland Complex
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J. New York Entomol. Soc. 110(1):127±141, 2002 DISTINCT GROUND BEETLE (COLEOPTERA: CARABIDAE) ASSEMBLAGES WITHIN A NEW YORK STATE WETLAND COMPLEX JAMES K. LIEBHERR1 AND HOJUN SONG1,2 1Department of Entomology, Cornell University, Ithaca, New York 14853-0901 U.S.A; and 2Current address: The Ohio State University, Department of Entomology, Museum of Biological Diversity, Columbus, Ohio 43212 U.S.A. Abstract.ÐCarabid beetle communities were compared for adjacent marsh and bog biotopes at the McLean Bogs Preserve, Tompkins Co., New York by means of pitfall-trap sampling. Though the sampled marsh and bog habitats were only 200 m distant, with the umbrotrophic bog isolated from the marsh/fen complex by a Wisconsin-aged glacial esker of only 7 m ele- vation, the resident wetland carabid species assemblages differed signi®cantly between the sites during the spring and summer seasons. Of 62 species observed in the wetlands, 36 were found exclusively in the marsh biotope, 17 were exclusive to the bog site, and only 9 were found at both sites. This level of wetland habitat ®delity was maintained in spite of potential colonization of the two sites each spring by adult beetles dispersing from overwintering sites in surrounding forest edge habitats. Pitfall sampling found 59 native carabid species, of which 52 were found during a survey conducted from 1916±1925, suggesting that the McLean Bogs Preserve sup- ports locally resident populations for the vast majority of carabid species found during this study. The McLean Bogs Preserve supports geographically southern, peripheral populations of the bog-specialist Platynus mannerheimii Dejean, as well as four marsh/fen-inhabiting speciesÐ Trechus crassiscapus Lindroth, Bembidion muscicola Hayward, B. praticola Lindroth, and Bra- dycellus semipubescens LindrothÐemphasizing the role this preserve plays in maintaining the distributional ranges of both bog- and marsh-resident taxa. The distinct faunas observed in these two proximate biotopes clearly illustrate that comprehensive conservation of the carabid beetle fauna of northeastern North America should involve preservation of a variety of wetland types. Key words: ground beetles, umbrotrophic bog, fen, microhabitat, community The degree to which species utilize only particular microhabitats in a landscape profoundly impacts how preserves should be con®gured and managed to conserve biotic diversity. For wetland biotopes, the special association of particular species with particular habitat types has been demonstrated for European mires, or bogs (Kvamme, 1976; Butter®eld and Coulson, 1983; Holmes et al., 1993; Batzer and Wissinger, 1996). New World bogs have been much less comprehensively studied, with the results displaying a variety of trends. Rosenberg et al. (1988) found a high level of habitat speci®city, but relatively low levels of taxonomic diversity for chi- ronomid midges in Ontario peatlands. Conversely, Runtz and Peck (1994), studying a late-successional bog in Ontario, report only a single bog-speci®c carabid beetle species±Platynus mannerheimii Dejean±among the 14 species observed. They char- acterized the bog-habitat species assemblage as derivative of adjacent forest habitats. FraÈmbs (1994) compared a Swedish plateau bog with various bog formations in Maine and New York, U.S.A., ®nding that highest carabid beetle diversity and abun- 128 JOURNAL OF THE NEW YORK ENTOMOLOGICAL SOCIETY Vol. 110(1) Fig. 1. A. Location of McLean Bogs Preserve in New York state, U.S.A. B. Local topog- raphy within Preserve near sample sites, redrawn from MSSCU (1926): ll 5 marsh trap transect, 11 5 Bog A trap transect. Contours indicate 10 ft (3.05 m) changes in elevation. dance were supported by bogs exhibiting a hummock-hollow mosaic of microhabi- tats, thereby allowing individuals to overwinter in the bog habitat. Such situations are obviously of maximal importance in expansive bogs characteristic of Canada and Maine (Johnson, 1985; Damman, 1995). As with earlier studies (Kvamme, 1976; Mossakowski, 1977), FraÈmbs found the European carabid beetle, Agonum ericeti (Panzer) to be an extreme bog-habitat specialist, most at home on the open sphagnum lawn of the Swedish Ryggmossen. His northeastern North American sampling did not indicate that any North American species exhibited such ®delity to bog habitats, though Agonum ericeti's sister species, Agonum belleri Hatch, has been long known as a sphagnum bog specialist of the North American Paci®c northwest (Hatch, 1933; Lindroth, 1966; Schreiner, 1978). Capitalizing on the advantages associated with a long-term ecological preserveÐ access to a variety of well-conserved habitat types (Needham, 1921), and an histor- ical record of taxonomic diversity (Members of the Scienti®c Staff Cornell Univer- sity [MSSCU] 1926, Leng, 1928)Ðwe undertook the study of a wetland complex consisting of adjacent fen-fed marsh and umbrotrophic bog microhabitats at McLean Bogs Preserve, Tompkins Co., New York (Fig. 1). We set out to answer two ques- tions: (1) what is the carabid beetle species composition in the fen and bog, and does this composition differ signi®cantly between the two habitats; and (2) have the species assemblages found in these habitats changed signi®cantly during the 75 years since the initial biotic survey? The preserve encompasses upland old growth hardwood forest, a complex of fens and ponds fed by runoff and springs ¯owing through glacial deposits, and various acidic bogs, including a topographically isolated umbrotrophic bog, plus a second bog that grades into surrounding marshland via wooded swamp. The isolated um- brotrophic bog and fen-stream fed marshland are separated by an esker ridge ap- proximately 100 m wide and7minheight, permitting comparable sampling on a 2002 WETLAND GROUND BEETLE ASSEMBLAGES (COLEOPTERA) 129 local scale to determine whether any differences in the biota of these microhabitats persist in the face of extreme geographic proximity. We focused on the carabid beetle assemblages associated with the umbrotrophic bog and alkaline marshlands. Carabid beetles offer the advantages of an extensive literature on taxonomy, biology, and habitat preference (e.g., Lindroth, 1945; 1961±1969a), and relatively high numerical abundance within wetland habitats (e.g., Runtz and Peck, 1994). We demonstrate that signi®cant differences exist between carabid assemblages occupying the bog and marshland habitats at McLean Preserve, with both habitat types supporting geograph- ically peripheral populations of carabid species. We also report that the species as- semblages found in this study are consistent with species reported from the preserve 75 years ago. These ®ndings establish for North America the importance of pre- serving a variety of wetland habitat types in situations such as the McLean Bogs Preserve, in order to comprehensively conserve the breadth of taxonomic diversity across the Carabidae, and by extension, other less well-studied wetland insect groups. MATERIALS AND METHODS Carabid beetle sampling was undertaken at the McLean Bogs Natural Area, a 40.5 hectare old-growth preserve situated in the Beaver Creek drainage, extreme north- eastern Tompkins Co., New York (428329480N, 0768169010W, Fig. 1A). The preserve centers on an alkaline marsh biotope surrounding Mud Pond (Fig. 1B). Both surface- fed streams and springs associated with glacial deposits drain into the marsh and pond. Demand for carbon dioxide in Mud Pond periodically removes all CO2 from solution, with resultant deposition of marl characterizing portions of the pond basin. Alkaline conditions (pH 5 8.4±9.4) have been reported in Mud Pond in August (Chamot and Georgia, 1926). Due to impoundment by a glacial esker, an umbro- trophic kettlehole bog±Bog A (Fig. 1B)±lies within 200 m of Mud Pond. A second transitional or oligotrophic bog (Johnson, 1985)±Bog B±drains circuitously into Ar- gus Brook, which lies at the north end of the basin occupied by Mud Pond. Hydrogen ion concentrations are such that pH values range from 3.7±4.4 at various times in the bogs (Chamot and Georgia, 1926). We conducted pitfall sampling at a marsh site on the northwest margin of Mud Pond (Fig. 1B), and a bog site near the northeast margin of Bog A. Five 9.4 cm diameter pitfall traps, covered by a suspended plastic plate, were arrayed at 3±5 m intervals (FraÈmbs, 1994). Each transect started at the forest edge and extended into the respective wetland habitat. Each trap was ¯anked by two 0.3 m long plastic sections of lawn edging, placed 1808 to each other, the cardinal direction determined by roots surrounding the pitfall cup; i.e., contingent on the most local conditions. The forest-edge trap was placed at the extreme margin of terra ®rma forest soil that was rarely inundated. The four wetland traps at each site were placed in the marsh or in the sphagnum carpet of the bog, either under the canopy of emergent shrubs, or along the edges of hummocks, thereby minimizing ¯ooding of the traps by rising water. Traps were half-®lled with ethylene glycol (1999) and propylene glycol (2000), and emptied on an approximate weekly schedule (shortened or lengthened slightly depending on weather conditions). Trapping was initiated 10 June 1999 and continued until 12 September 1999. Based on results of the ®rst year, a second spring season of sampling was started 19 April 2000 and ®nished 12 June 2000, thereby 130 JOURNAL OF THE NEW YORK ENTOMOLOGICAL SOCIETY Vol. 110(1) producing data for the two sites that span ®ve months characterized by the warmest nighttime temperatures over the year. The marsh biotope surrounding Mud Pond consists of a shrubby quaking matÐ locally called a grass bog (Needham and Claassen, 1926)±consisting of tussock- forming grasses and sedges. The dominant shrubby vegetation on the mat includes speckled alder (Alnus rugosa), red-osier dogwood (Cornus sericea), and silky willow (Salix sericea). Bog A is surrounded by tall trees±beech (Fagus grandifolia), hem- lock (Tsuga canadensis), and sugar maple (Acer saccharum) dominating±with a well-developed root mat resulting in a hummocky shoreline.